Mobile radios are often used in applications where it is highly desirable for more than one user to operate a single radio transceiver. Public safety organizations, such as firefighters and paramedics, rely on mobile radios in their emergency vehicles to allow the occupants to perform a number of tasks critical to their life saving work. For instance, for a paramedic team in a mobile trauma unit vehicle, the paramedic/driver of the vehicle needs control of the radio to communicate with a dispatcher directing the unit to the location of the trauma patient and to the available hospital. Once a patient is onboard the vehicle, the paramedics performing treatment in the patient area need control of the mobile radio to rapidly notify the hospital of the condition of the trauma patient and to consult with an emergency room physician to obtain orders regarding patient treatment. Similarly, a firefighter/driver and the commander-in-charge setting up a command post at the scene of a fire both need control of the mobile radio from different locations in order to rapidly and effectively perform their life saving tasks. It is thus desirable to have a radio system having the capability for two individuals in separate locations to operate a single radio transceiver.
Mobile radios are typically operated through use of a control head that is remotely connected to a radio located in the vehicle. Known higher tier mobile radio transceivers support dual control head capability. This dual control head capability enables two heads to operate a single radio transceiver. FIG. 1 shows schematically an exemplary known higher tier radio system designed for use with two control heads. Mobile radio system 10 has a radio transceiver 12 coupled to two control heads 14, 16 via a bus 26. Bus 26 is preferably a digital data bus. Radio systems such as system 10 also provide analog voice communication on an analog bus (not shown), such voice communication and bus being known to one of ordinary skill in the art. Control heads 14, 16 are provided for operating the transceiver 12. Preferably, control heads 14, 16 are identical units. Each of the control heads 14, 16 includes a display 20 for presenting the status of the transceiver 12 to a user. The display 20 is preferably an LCD type that provides a presentation to a user of alphanumeric characters and graphic symbols (e.g., the selected radio channel number and status icons). Each control head also provides a control to enable a user to selectively change the backlighting of the LCD display according to the user's preference for the ambient light conditions. Control heads 14, 16 also typically include a plurality of controls for user management of functions of the transceiver 12 (e.g., entry buttons 22 and on/off/volume control knob 18 shown in FIG. 1). Buttons 22 may be programmable in the radio to serve certain user defined functions. Control heads 14, 16 also typically include a plurality of LED indicators and additional buttons, such as channel selector buttons (not shown for the exemplary control heads in FIG. 1).
As shown in FIG. 1, an input device 24 may be attached to an audio input jack of the control heads 14, 16 for enabling voice communication. Input device 24 is typically a microphone, a microphone/keypad combination, or a telephone style handset. In alternate embodiments, each control head may have a different type of input device 24, which is preferably a wired device, but alternately may be wireless. Control heads 14, 16 include an integrated audio speaker 28. The input device 24 may also provide a microphone and an audio speaker integrated as part of a handset. The input device is typically enabled only for half-duplex operation by a user. This half-duplex operation provides a listen-only mode and a talk mode such that a user can talk or listen using the device, but cannot do both at the same time. A push-to-talk button (PTT) (not shown) is typically provided on the input device 24 to select between these modes.
A speaker privacy mode feature may also be provided wherein a hookswitch control is provided on input device 24. For example, an operator using a telephone style handset for input device 24 can activate this privacy mode to enable the operator to listen to incoming audio on the handset speaker in privacy since the speaker on the control head is muted. Various other features are typically provided by the radio system and are known to one of ordinary skill in the art.
A drawback of the higher tier system shown in FIG. 1 is the significantly higher cost of a transceiver in this system compared to the cost of a lower tier mobile radio transceiver designed for use with a single head. FIG. 2 shows an exemplary lower tier mobile radio system designed for use with a single control head. As shown, a radio system 30 has a transceiver 32 coupled to a control head 14 via a digital data bus 34. A drawback of known lower tier systems is that these systems are designed to inhibit the use of more than one control head to operate the transceiver.
Radio system 30 also provides for sending audio communications to and from a user of the control head (e.g., voice communication from a user speaking into a microphone included in input device 24). The voice communication signals are typically coupled by means (e.g., analog signal bus) that is separate from data bus 34, between the control head 14 and transceiver 30. Alternatively, the voice communication signals could be converted to a suitable digital form prior to signal distribution.
Municipalities and other mobile radio purchasers typically have limited budgets for the purchase of needed mobile radio systems, so these purchasers need to receive the required radio system capability at an economical cost. Owners of a radio transceiver designed for operation with a single control head often desire to add dual control head capability without having to purchase a new radio transceiver. What is needed is a cost efficient method and apparatus to enable dual control head operation in a radio system designed to operate with one control head
Older mobile radio systems typically utilized analog communication between a radio transceiver and the control head. In modern mobile radio systems, most of the signal functions previously carried via analog electrical signals are currently being encoded into a digital format for communication on a digital bus between microprocessor controllers in the control head and the radio transceiver. This digital communication is typically encoded for particular protocols. What is needed is a method and apparatus for connecting two control heads to the same digital bus without disrupting communications.
The control heads in a radio system utilizing digital communication typically each sends an interrupt service request (“interrupt”) in response to user actions performed at the control head. Higher tier dual control head radio systems are typically designed to handle this multiple interrupt environment internally by programming the microprocessor software to support two control heads. What is needed is method and apparatus providing an interface module, coupled between a radio transceiver designed for use with single control head and two control heads, to mediate communication between these devices, such that each of the control heads is selectively enabled to operate the radio transceiver.
The control heads of mobile radio systems typically include a volume control (e.g., a knob on the head) for adjustment of the volume level and an audio speaker built into the head. Known radio systems may optionally provide a telephone-style handset or other device having an integrated speaker and being connected directly to the control head to enable voice communication. A drawback of a known higher tier mobile radio system having two control heads is that the system requires an additional external amplified speaker, having a volume control mounted thereon, to provide audio for one of the two control heads. For this known system, the audio fed to this external speaker's amplifier is derived from a constant level audio source. A user of this known system must access the area where this speaker is mounted, external to the control head, in order to control the volume of audio for one of the control heads. What is needed is a method and apparatus for a dual control head radio system that utilizes the volume controls and speaker integrated with each control head such that any additional speakers are not required. A user might desire having the option to add an external speaker for the control head. What is also needed is a system enabling use of this optional external speaker while allowing the audio level of this speaker to be adjusted by the corresponding control head volume control knob.